Question about a true damage of yasuo

I just lost a battle in one for all. After one death I checked the damage resourse, under the damage down by a player called totintug, there is lots of true damage called totintug and there is no icon for that damage. (like close to half of his damage is ture damage) I don't really know how the display works... So I just want to ask what damage is that? Because I get killed very quickly even with full tank building of the most gold earn of the team.